There is herein defined a control apparatus operable to control the opening and closing of downhole flow control devices. The apparatus includes first and second indexing modules, which are arranged in fluid communication with a respective downhole control device. Each of the modules includes two inlet ports and two outlet ports, where the inlet ports are each in fluid communication with one of two control lines. The first module is operable to open and close a first downhole control device on application of fluid pressure through the first control line and the second module is operable to open and close a second downhole control device on application of fluid pressure through the second control line.